Causes of Valley Fever in Dogs
Dog Breeds
In southwestern areas of the United States, particularly in dry desert regions, the fungus Coccidioides immitis lives naturally in the soils. During periods of drought, the fungus goes into a dormant stage. However following periods of rain, the fungus becomes a mold and releases spores into the air.
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Introduction
“Valley Fever,” or Coccidioidomycosis, is a respiratory and systemic fungal disease of dogs and people caused by infection with Coccidioides immitis. This fungus only thrives in dry, hot areas, especially in the southwestern United States, Mexico and a few parts of Central and South America. The fungus lives and grows several inches down in the soil, where it can survive high temperatures and low moisture. It becomes particularly infective after periods of rainfall, when it rises to the surface, sporulates and spreads in the air. Not all dogs exposed to the fungi succumb to clinical disease, but many do. When it becomes disseminated systemically (throughout the body), it is considered one of the most severe and potentially fatal fungal diseases in dogs, although it is uncommon even in endemic areas.
Causes of “Valley Fever” in Dogs
In the deep southwestern areas of the United States, particularly in arid desert regions of Arizona, California and Texas and less commonly in New Mexico, Nevada or Utah, the fungus Coccidioides immitis persists naturally several inches down in the soil. During periods of drought, the fungi exist in a dormant stage. Following periods of rainfall, the fungi sporulate and release many infectious stages of the organism called “arthroconidia,” that spread by wind, dust and rain storms. Release of spores in endemic areas is also commonly associated with earthquakes and demolition or other large land construction projects where substantial soil disruption occurs. Inhalation of even 10 or fewer of these highly infectious spores can cause clinical disease. However, many exposed dogs will not develop clinical signs; they may have asymptomatic infections with very mild, undiagnosed respiratory infection, or they may develop immunity without ever showing clinical signs.
Why some dogs are able to resist clinical infection while others develop life-threatening disease is not well understood in current circles of veterinary medicine. It is thought that immunosuppressed or immunocompromised animals are at a greater risk of developing systemic disease from exposure to and infection by this fungus. Older animals also seem to be at higher risk, as do those with poor nutritional support.
Symptoms and Types
Overview and Facts